Due to the proliferation of personal computers, the widespread acceptance of the Internet, and the advent of the Information Age, there is a virtual explosion in the amount of digital data transmissions. Currently, one common method for transmitting and receiving digital data involves the use of telephone modems. A telephone modem is used to transmit digital data generated by a computer to an intended destination over standard telephone lines. The same modem also can receive digital data from a telephone line. This setup enables computers to gain access to the Internet and other on-line services over standard telephone jacks. Although this form of communications is convenient, it is painfully slow because telephone lines simply consist of pairs of twisted copper wires. These lines were primarily designed to carry analog voice signals rather than digital data. As such, telephone lines are bandwidth limited, and the rate at which digital data can be transmitted is relatively quite slow. It can take several minutes or even hours to download picture, audio, and video files via standard telephone modems. Hence, telephone modems are not ideally suited for conveying video (e.g., teleconferencing, movies, etc.), graphics (e.g., computer-aided design, medical imaging, simulations), or multimedia applications.
A faster medium for high-speed communications entails the use of dedicated computer networks, whereby computers are interconnected to form local area networks or wide area networks (LAN/WAN). However, the downside to this approach is the high cost of purchasing, routing, and maintaining the requisite interconnecting coaxial and fiber lines. Furthermore, highly skilled network administrators are necessary to monitor the network in order to keep it operational. In addition, expensive networking equipment (e.g., routers, hubs, repeaters, concentrators, servers, bridges, etc.) must be purchased and installed. Hence, the advantage of having faster data communications and higher bandwidth comes at a steep price. Furthermore, it is prohibitively expensive to set up dedicated computer networks amongst individual homes.
There is, however, another medium which is widespread and already in place and which also has a very high bandwidth suitable for transmitting vast amounts of information This medium is the cable TV (CATV) networks. CATV is comprised of coaxial and fiber optic cables which have very high transmission capacity. These CATV lines connect a central station or headend to set-top boxes in everyone's homes. CATV was primarily limited to being only a one-way transmission medium, whereby TV signals were broadcast from a headend terminal, over the CATV network, to a host of subscriber units. After down conversion, the RF TV signals are eventually displayed on a subscriber's television set.
Instead of simply broadcasting TV signals, it is feasible to use these same CATV networks to provide high capacity two-way data communications. One ideal implementation, as adopted by the present invention, is to use a Cell-based Asynchronous Transfer Mode (ATM) approach. ATM is ideally suited for supporting services requiring real-time functionality due to its precise control over delay and jitter, such as video teleconferencing, game playing, voice communications, etc. At the same time, ATM is also well suited for handling data transmissions which are not as delay sensitive (e.g., Internet services). In addition, the nature of an ATM cell based system allows for other multimedia applications to be upgraded without requiring iterative changes to the underlying structure. Hence, ATM offers several advantages over competing prior art systems which attempt to deliver digital data by using the CATV network as an end-to-end solution by converting it into a shared media local area network (LAN). Some prior art end-to-end CATV shared media LANs include Ethernet, Carrier Sense Multiple Access (CSMA), Collision Detect (CD), Token Ring, and Fiber Distributed Data Interface (FDDI) protocols. The main problem faced by these different schemes lies with dealing and handling time-critical data. Because much of the data being conveyed is highly delay sensitive, these prior art systems typically do not provide tight enough tolerances which are required in order to adequately support integrated services. As such, they fall far short of providing the degree of services that could potentially be derived from CATV networks. These problems associated with prior art systems can be overcome by using an isochronous ATM approach. For instance, Ethernet packets can be converted into ATM cells for transmission over the CATV network.
Unfortunately, ATM switches are typically restricted in the total number of addresses which can be handled. Since each subscriber terminal unit (STU) coupled to the CATV network has to have its own unique address, the total number of STUs which can be supported by a common ATM switching fabric is limited. The present invention provides one way to overcome this addressing restriction.
Another problem which must be overcome in converting a CATV system into a data highway relates to the fact that CATV networks have historically been limited to being a public service provider. The same content was indiscriminately conveyed to all the receiving stations. This scheme works well for public transmissions, such as television broadcasts. However, it fails utterly when dealing with transmissions that are sensitive or confidential in nature (e.g., a professional working at home). Hence, there is a need for some mechanism to ensure that specific data is securely routed to only the intended recipient STU or a specific group of STUs. Furthermore, it would be prudent to include some mechanism for filtering data to prevent intentional or benign errors from causing the entire CATV to break down. The present invention solves both these issues.
Yet another problem is that whereas some data transmissions are extremely delay sensitive, other data might not be as time critical but require a high degree of accuracy. For example, telephone communication requires that the corresponding data be transmitted rapidly so that the parties can carry on conversations with imperceptible lags. In contrast, video data can be routed as bandwidth permits because users can suffer slight delays in receiving the data with minor perceptible distortions, but the data should be error-free to ensure a high quality picture. Thus, it would be beneficial if a user could somehow tailor their reception to meet the specific needs of their current application. The present invention allows a user to select a Quality of Service that best meets the current needs.
The present invention offers solutions to all the problems described above so that CATV networks can function as a flexible, effective, economic, and fully integrated two-way multimedia bearer system, thereby granting immediate support for Internet services, traditional voice telephony, and digital video services.